The invention relates to a method for the regulated humidification and temperature control of a gas mixture in an inner chamber of an incubator, in which the inner chamber is sealed off from the surroundings by a housing.
The invention also relates to an incubator with regulated humidification and temperature control of a gas mixture in an inner chamber which is sealed off.
Incubators serve for storing samples in their inner chamber under predefined conditions, such as a certain temperature and air humidity, and in a defined gas atmosphere. A typical inner chamber temperature varies in a range of 20-40 degrees Celsius at a humidity of the gas mixture in the inner chamber in the range of 70-90%. Furthermore, so-called “shaking incubators” are known, which provide ideal conditions for cultivation processes.
Moisture regulation in incubators, in particular shaking incubators, is important to reduce evaporation, in particular in the case of long-lasting cultivations of up to 14 days and very small culture liquid volumes, in particular in microtiter plates. High evaporation leads to a change of the cultivation medium and influences the growth and the metabolism of the cells.
A reduction in the evaporation is achieved by humidification of the gas mixture in the inner chamber of the incubator. Here, the principle applies that the higher the humidity of the gas mixture in the inner chamber, the lower the evaporation of the culture medium. However, at very high humidity values of over 85%, there is the risk of moisture condensing out on inner surfaces of the incubator because of the temperature distribution not being completely homogeneous. Such moisture regions which form as a result of the condensing out constitute potential sources of contamination.
DE 10 2006 022 652 B4 discloses a shaker incubator and a method for the humidification and temperature control of the air in the inner chamber of the incubator, in which moisture is fed to the air from a moisture source of a humidification device, and the temperature of the air is controlled via an incubator heater and/or incubator cooler. As a result of two air circuits which are separate from one another, the humidity of the air in the inner chamber can be regulated using a conventional humidification device almost independently of the temperature regulation with the aid of the incubator heater and/or cooler. Use is made of a temperature-regulated water bath as a humidification device in a known way. The humidity in the inner chamber is measured by a humidity sensor. The regulation of the moisture is realized by regulation of the air stream in the first air circuit, which has the humidification device, and by regulation of the heating element of the water bath.
It is not possible to actively reduce the humidity by the known incubator and the method for the regulated humidification and temperature control of the air in the inner chamber of the incubator. For this purpose, moisture has to be removed from the air.
Adolf Kühner AG Dinkelbergstr. 1, 4127 BIRSFELDEN (Basel), Switzerland produces shaker incubators with an optional humidity regulator, inter alia under the designation ISF1-X. In order to increase the humidity of the gas mixture, a water bath is arranged in the inner chamber of the incubator. The temperature in the water bath is increased by an electric heater and increases the humidity of the gas mixture in the inner chamber by evaporation of the water. To actively reduce the humidity, a cooling circuit of a compressor cooler is integrated into the incubator. The evaporator of the cooling circuit is situated in the inner chamber as a condensation surface. The moist gas mixture condenses on the evaporator which is provided such that the condensed water drips or flows back into the water bath. The regulation is realized with the aid of a capacitive sensor for measuring the actual value of the humidity of the gas mixture in the inner chamber. A digital PID regulator increases the humidity by evaporation of water from the electrically heated water bath if, because of the continuous reduction in the humidity at the evaporator, the actual value is less than the target value. The continuous heat dissipation at the evaporator is maintained by controlling the temperature of the gas mixture to a desired value of the inner chamber temperature by a heater (www.kuhner.com/de/produkte/schuettelmaschinen/inkubatoren/isf1-xhtml, downloaded on 13.02.2017).
In the incubator ISF1-X of the company Kühner AG, the compressor cooler performs two tasks. It can lower the inner chamber temperature and reduce the humidity of the gas mixture in the inner chamber. However, incubators, in particular shaking incubators, are often operated at a constant inner chamber temperature in a range of 32-37 degrees Celsius by their users so that lowering of the inner chamber temperature is not necessary. But, the cooling unit is necessary for the humidity regulation.